For many years, automobiles and other vehicles have been provided with independent suspension systems which absorb road shocks and other vibrations to provide a smoother, more comfortable ride for the occupants of the vehicle.
In suspensions of this type, a stabilizer is often incorporated to increase the roll rigidity and improve the steering stability of the vehicle. Typically, the stabilizer is a rod-like, elastic member having a central torsion bar portion oriented laterally of the vehicle and two integral arm portions provided at each end of the central rod portion forming substantially the shape of three sides of a polygon. The central rod portion, generally adjacent to each arm portion, is rotatably supported about a longitudinal axis from the vehicle body and each of the ends of the arms are coupled to a suspension arm by a connector link. When the vehicle is subjected to rolling, for example, by centrifugal force, the arm portions pivot relatively about the longitudinal axis of the central rod portion causing torsion forces which, through the arms, urge the suspension arms of the vehicle toward their normal position.
These types of torsional stabilizer bars as well as other suspension elements have proven useful in vehicles for many years and examples of suspension links for vehicle suspensions or stabilizer bars of various configurations are shown in British Patent 533,159 and U.S. Pat. Nos. 2,027,577, 2,094,142, 2,555,141, 2,660,449, 2,661,969, 2,950,774, 2,961,253, 3,181,885, 3,205,967, 3,212,387, 3,726,542, 3,733,087, 4,066,278, 4,143,887, 4,203,615, 4,621,831, 4,664,408, and 4,781,364. Stabilizers act in a manner that when a pair of left and right wheels differ in level from each other due to a cornering maneuver, the vehicle body will be prevented from excessive rolling or leaning to either side by torsional or other resistance produced in the stabilizer bar.
In response to the driving public demands, more "sporty" cornering capability, automotive designers have increased the diameters of conventional stabilizer bars. Although this modification beneficially increases roll stiffness, it also degrades the ride quality in many cases. While designers have thought to enhance the function of stabilizer bars in a variety of ways, such as the adjustable suspension stabilizer bar shown in U.S. Pat. No. 4,648,620, very little attention has been paid to other elements of the suspension system. For example, many improvements have been made in shock absorbers and tire constructions as well as various independent suspension arms and new designs. For the past twenty years there has been substantially no improvement or change in the attachment links or connectors for the various elements of the suspension system.
Vehicle supension system connectors such as the stabilizer bar attachment have essentially remained unchanged for many years. These attachments as well as many other suspension system attachments experience a variety of environments which result in corrosion and failure during the useful life of the vehicle. The lifetime of such an attachment will depend upon its components ability to maintain their original dimensions and material characteristics. Because these vehicle components are primarily utilized on the under carriage of a vehicle, they are subjected to the harsh effects of rain, salt and sleet.
Typically, these attachments are assemblies of many different components which must be manually assembled during the production of a vehicle. A stabilizer link bar attachment generally falls into one of two broad categories, a bolt-type construction or a stud-type construction. In the bolt-type construction, a suitably dimensioned bolt is used to connect the stabilizer bar to the vehicle suspension arm. The presently used bolt-type construction includes seven steel parts which are subject to the corrosive effects of the environment, primarily road salts and moisture. The attachment includes several rubber bushing or grommet portions which, are to a lesser degree, affected by the same environmental hazards. When assembled, the bolt-type link has its head and retaining nut in engagement with a pair of outer washers which are cushioned by pliable bushings or grommets engaging the exterior surfaces of the stabilizer bar arms and the vehicle suspension arms. A pair of similarly shaped grommets engage the interior surfaces of the respective vehicle elements and are in engagement with a pair of inner washers which are maintained at a predetermined spaced distance by a cylindrical sleeve mounted on the shaft of the bolt. Therefore, typically, this type of construction includes eleven elements, seven of which are made of steel. Typically the steel is treated with a conventional plating to assist in the prevention of corrosion. However, all of the abutment points, primarily between the bolt head or retainer nut and the respective adjacent washer and between the ends of the spacer sleeve and adjacent interior pair of washers. Spaces between these elements permit the introduction of road salts and moisture which lead to corrosion and degradation of the part. A high incidence of severely rusted bolt components has been found in vehicles during the course of their use. Depending upon the particular climate in the area in which the vehicle is used, more or less corrosion in the metal components have been noted.
While corrosion has often caused premature failure of the attachment assembly during normal use, it is often necessary to change the rubber bushings or grommets which become incapable of performing their intended function due to the environmental degradation. In this situation, the attachment must be disassembled to replace the worn bushing elements and quite often during this operation the bolt portion is broken due to the torsional forces during the attempt at disassembly or must be cut apart to make the disassembly possible.
The stud-type attachment construction is essentially the same as the bolt-type construction but includes two threaded ends requiring the use of an additional retainer nut on the "top end" of the stud. In this stud-type construction, it is necessary to permit means to restrain the stud from rotating during tightening of the nut. Therefore, in this type of construction, a spacer sleeve generally cannot be used since the central portion of the stud must be grasped to prevent its rotation. Therefore, much more expensive "spacing means" must be provided. One form of a spacing mechanism is to create flanges at predetermined points along the shaft of the stud which maintain a predetermined dimension between the interior pair of washers.